Cooled turbine blade

ABSTRACT

A turbine blade is cooled internally by air discharged through perforations in a liner toward the interior of the blade wall. The liner is spaced from the blade wall by ribs on the wall extending spanwise of the blade. The ribs increase in height toward the blade tip so that spanwise-extending diverging passages for discharge of the cooling gas at the tip of the blade are provided. The liner is of a relatively high conductivity material such as a cuprous nickel alloy. The exterior of the liner is artificially roughened to increase the absorptivity of the liner to radiated heat. The blade has a base into which the liner extends so as to conduct some of the heat through the liner into the base, which is relatively isolated from the hot motive fluid to which the blade is subjected.

United States Patent ["191 McCormick 416/96 Aspinwall Apr. 23, 1974COOLED TURBINE BLADE Primary ExaminerEverette A. Powell, Jr. [75]Inventor: Robert H. Aspinwall, Zionsville, Ind. Attorney Agent orfirm-Paul Fltzpamck [73] Assignee: General Motors Corporation,

Detroit, Mich. [57] ABSTRACT Filed; 8- 30, 1972 A turbine blade iscooled internally by air discharged 21 A L N z 284 716 throughperforations in a liner toward the interior of PP 7 the blade wall. Theliner is spaced from the blade wall 1 by ribs on the wall extendingspanwise of the blade. [52] [L8, Cl. 416/97, 415/1 15 The ribs increasein height toward the blade tip 50 that [51 Till. Cl. F01d 5/18panwise-extending diverging passages for disgharge 0f Field 0f sell'ch/9 the cooling gas at the tip of the blade are provided.

415/115, 116 The liner is of. a relatively high conductivity materialsuch as a cuprous nickel alloy. The exterior of the References Citedliner is artificially roughened to increase the absorptiv- UNITED STATESPATENTS ity of the liner to radiated heat. The blade has a base2,787,441 4/1957 Bartlett 416/92 which the liner extends as to'conduc2,873,944 2/1959 Wiese et a1. 416/92 the heat through h liner into thebase, which is rela- 2,894,719 7/1959 Foster 416/92 tively isolated fromthe hot motive fluid to which the 3,032,314 5/1962 Davidml 416/96 Xblade iS subjected. 1 3,314,650 4/1967 4 Claims, 6 Drawing Figuresimproved means for cooling such blades, to increase themaximumtemperature level of the engine in which they are employed. The reasonfor high temperature levels is greater efficiency and a lighter weightand more compact power plant.

It is important that cooling'be as effective as possible so as tominimize loss of power or efficiency due to the provision of cooling airor other medium for cooling the blades.

My invention is directed to improved structure for internally cooling aturbine blade orvane of a nonporous wall type. The preferred structureof my invention involves a liner from which cooling air is spoutedthrough small perforations toward the wall of the blade,

the liner being spaced from the blade wall by ribs extending inward fromthe 1W3. Such structures are known. According to my invention, however,the liner ismade of a material of-relativelyhigh conductivity suchascuprous nickel material and thus has greater than usual ability toconductsome heat out of the airfoil into the blade base. Also, transferof heat by radiation from the blade wall to the liner is improvedbyproviding a roughsu rface on the liner to increase the thermalabsorptivity of .the liner.

The principal objects of my invention areto. provide improved means forcoolingflow-directing members forhigh temperature machines, to provide acooled blade which is of simple and readily fabricated structure, and toprovide a system having maximum effectivenessfor cooling a blade byinternal convection and radiation, as distinguishedfrom transpirationcooling.

The nature of my invention and its advantages will be clear to thoseskilled in the art from the succeeding detailed description of preferredembodiments of the invention and theaccompanying drawings thereof.

FIG. 1 is an elevation view of aturbine blade.

direct contact with the motive fluid. The'base 6 comprises a hollowstalk 7 and a dovetail or serrated root 8 adapted for mounting in aturbine rotor structure. Referring particularly to FIG. 2, the hollowblade 3 is defined by a wall 9 and is illustrated as having a suitablecambe'red airfoil configuration, having a leading edge 10, a trailingedge 11, a convex face 12, and aconcave face 14. The blade wall definesan internal chamber 15 of generally airfoil shape, and the tip of theblade at 16 is open. The blade stalk 7 defines anentrance 18 for coolinggas, ordinarily compressor discharge air in a gas turbine engine. Ahollow sheet metal liner 19, the surface of which maybe considered to beparallel ina roughway to thewall 9, is disposed within the chamber 15.

As illustrated in FIG. 3, the upper end of the liner is closed by ajunction between the two side walls of the liner at 20. The base end ofthe liner may be disposed in slots 22 in the wall of the stalk andsuitably fixed there. This is beneficial to conduction of heat from theliner into the blade stalk. Since the stalk first receives the coolinggas and is not in direct contactwith the hot FIG. 2 is a much enlargedtransverse section of the,

blade taken on the plane indicated by'the line-22 in' FIG. 1.

FIG. 3 is a somewhat enlarged longitudinal section of the blade taken inthe in FIG. 2.

FIG.4 is a greatly enlarged fragmentary view of a plane indicated by theline 3-3 portion of the blade wall and liner taken in a plane exbase 6.The platforms of adjacent blades define oneboundary of thehotmotive'fluid path through a cascade of blades. The platform isolates thebase 6 from motive fluid, it is normally much cooler than the blade wall9.

The interior of the blade wall 9 bears generally parallel ribs 23 whichextend into contact with the blade liner and which, as will be apparentfrom FIG. 3, increase in height toward the tip of the blade."As aresult, spanwise-extending passages 24 defined between the blade wall9and the liner 19 and] bounded by the ribs 23 increase in depth and-areatowards the tip of the blade to maintain a more or less constantvelocity of flow along the passages as the volume of flow increases.Cooling air which enters the opening 18 in the open blade base end ofthe liner is discharged through a multiplicity'of small perforations orspouting holes 26 distributed along each passage 24. The liner I9 isbonded to the ribs 23 by brazing, diffusion bondin'g, or other suitableprocess, as indicated at the points27 in FIG.

a cuprous nickelalloy having relatively high thermal conductivity.

The interior of the blade wall and the ribs 23 ordinarily are left witha relatively smooth finish such as results from the manufacture. Theliner, onthe other hand, is artificially roughened to provide higherheat absorptivity as shown more clearly in FIGS. 4 and 6. Preferably,this roughening is in the form of contiguous parallel V-grooves 30preferably of about included angles. This roughness may be produced byetching or by machining or by a process of, rolling the sheet as desired. The relatively smooth surface of the blade wall gives it a graybody characteristic, whereas the rough surface of the liner gives itmore of a black body characteristic. The relatively higher absorptivityof the liner and the relatively higher emissivity of the wall improvethe liner. This is not the major means for removal of 'which'may be l,0OF. hotter than the cooling air in the interior of the liner. The innersurface of the blade wall is substantially cooler than its outersurface, the ribs cooler yet, and the liner 19 still cooler. Because ofthe high heat transmitting characteristics of the liner, it is moreeffectivein transmitting heat from the ribs to the cooling air,providing additional .effective surface for convection cooling. In thebonded joint there is good transfer of heat from the ribs to the liner.Since the liner is a good heat conductor, it also is instrumental inconducting heat toward the base of the blade into the area which isremote from the motive fluid stream above the platform 4. Also, becauseof the greater absorptivity of the ridged or roughened surface of theliner, the transfer of heat from the wall by radiation to the linerisimproved. The liner, of course, is cooled by the cooling air flowingwithin the liner and through the holes 26 through the liner as well asby the air flowing through the passages 24 which air, of course,receives most of its heat from the wall 9.

It may be helpful to give an example of preferred dimensional values ina blade as described above. The blade may be considered to have a chordof about l inches, with a rib every 50 mils (a mil being a thousandth ofan inch), the ribs being 10 mils wide, and the air holes 26 about 6 milsin diameter. The distance from the liner to the blade wall increasesfrom about 12 mils to about 40 mils from base to tip of the blade, theblade wall is about 40 mils thick, and the liner is about 10 mils thick.The ridges or grooves 30 on the liner are about 3 mils deep. Suchdimensions are subject to change, of course, depending upon the natureof the particular installation and exercise of engineering analysis.

The blade 2 may be cast integrally in one piece, following, for example,the techniques described in Mc- Cormick US. Pat. No. 3,192,578, July 6,1965, or the airfoil and base may becast separately and joined by awelding or diffusion bonding operation. Or, if desired, the structuremaybe cast in two parts which are then bonded together as illustratedgenerally in FIG. 6. The blade 34 of FIG. 6 is made of two parts 35 and36, each defining one side of the blade or airfoil 38, of the platform39, of the stalk 40, and of the root 42. These are united along ajoining surface 43 which ordinarily, in practice, might approximatelyfollow the mean camber line of the blade. The ribbed interior of theblade and other details are not indicated in FIG. 6.

It should be apparent to those skilled in the art that I have conceiveda significant improvement in the principles of internal cooling ofblades, giving greater efficiency in the use of cooling air and greateruniformity of temperature throughout the blade. 7

The description of preferred embodiments ofthe invention for the purposeof explaining the principles thereof is not to be considered as limitingor restricting the invention, since many modifications may be made bythe exercise of skill in the art.

I claim:

1. An internally-cooled flow-directing member for a turbomachinecomprising, in combination, a hollow airfoil having an external walldefining an internal chamber, a liner disposed in the airfoil and spacedfrom liner between the ribs, the inner surface of the wall having arelatively smooth finish forhigh heat emissivity and the outer surfaceof the liner having a relatively rough finish for high heatabsorptivity, and the liner being made of a material of relatively highcoefficient of thermal conductivity as compared to the airfoil.

2. An internally-cooled flow-directing member for a turbomachinecomprising, in combination, a hollow airfoil having 'an external walldefining an internal chamber, a liner disposed in the airfoil and spacedfrom the wall, the liner'having an inlet for a cooling gas and definingdistributed perforations for discharge of the gas toward the wall, theairfoil defining an outlet for the cooling gas, the wall bearinginternal ribs extending spanwise of the airfoil and bonded to the liner,the inner surface of the wall having a relatively smooth finish for highheat emissivity and the outer surface of the liner having a relativelyrough finish for high heat absorptivity, the liner being made of amaterial of relatively high coefficient of thermal conductivity ascompared to the airfoil.

3. An internally-cooled flow-directing member for a turbomachinecomprising, in combination, a hollow airfoil having an external .walldefining an internal chamber, a liner disposed in the airfoil and spacedfrom the wall, the liner having an inlet for a cooling gas and definingdistributed perforations for discharge of the gas toward the wall, theairfoil defining an outlet for the cooling gas, the inner surface of thewall having a relativelysmooth finish for high heat emissivity and theouter surface of the liner having a relatively rough, finish for highheat absorptivity, the liner being made of a material of relatively highcoefficient of thermal conductivity as compared to the airfoil; theairfoil having a base isolated from the flow passing by the airfoil andincluding an inlet for the cooling gas, the liner extending into thebase.

4. An internally-cooled flow-directing member for a turbomachinecomprising, in combination, a hollow airfoil having an external walldefining an internal chamber, a liner disposed in the airfoil and spacedfrom the wall, the liner having an inlet for a cooling gas and definingdistributed perforations for discharge of the gas toward the wall, theairfoil defining an outlet for the cooling gas at the tip of theairfoil, the wall bearing internal ribs extending spanwise of theairfoil and engaging the liner, the ribs increasing in height toward theairfoil tip so that cooling gas passages diverging toward the airfoiltip are defined by the wall and liner between the ribs, the innersurface of the wall having a relatively smooth finish for high heatemissivity and the outer surface of the liner having a relatively roughfinish for high heat absorptivity, the liner being made of a material ofrelatively high coefficient of thermal conductivity as compared to theairfoil; the airfoil having a base isolated from the flow passing theairfoil and including an inlet for the cooling gas, the liner extendinginto the base.

* a: a 1k

1. An internally-cooled flow-directing member for a turbomachinecomprising, in combination, a hollow airfoil having an external walldefining an internal chamber, a liner disposed in the airfoil and spacedfrom the wall, the member having an inlet for a cooling gas at one endof the airfoil and an outlet for the cooling gas at the other end of theairfoil, the wall bearing internal ribs extending spanwise of theairfoIl and engaging the liner, the ribs increasing in height toward thecooling gas outlet so that cooling gas passages diverging toward theairfoil outlet are defined by the wall and liner between the ribs, theinner surface of the wall having a relatively smooth finish for highheat emissivity and the outer surface of the liner having a relativelyrough finish for high heat absorptivity, and the liner being made of amaterial of relatively high coefficient of thermal conductivity ascompared to the airfoil.
 2. An internally-cooled flow-directing memberfor a turbomachine comprising, in combination, a hollow airfoil havingan external wall defining an internal chamber, a liner disposed in theairfoil and spaced from the wall, the liner having an inlet for acooling gas and defining distributed perforations for discharge of thegas toward the wall, the airfoil defining an outlet for the cooling gas,the wall bearing internal ribs extending spanwise of the airfoil andbonded to the liner, the inner surface of the wall having a relativelysmooth finish for high heat emissivity and the outer surface of theliner having a relatively rough finish for high heat absorptivity, theliner being made of a material of relatively high coefficient of thermalconductivity as compared to the airfoil.
 3. An internally-cooledflow-directing member for a turbomachine comprising, in combination, ahollow airfoil having an external wall defining an internal chamber, aliner disposed in the airfoil and spaced from the wall, the liner havingan inlet for a cooling gas and defining distributed perforations fordischarge of the gas toward the wall, the airfoil defining an outlet forthe cooling gas, the inner surface of the wall having a relativelysmooth finish for high heat emissivity and the outer surface of theliner having a relatively rough finish for high heat absorptivity, theliner being made of a material of relatively high coefficient of thermalconductivity as compared to the airfoil; the airfoil having a baseisolated from the flow passing by the airfoil and including an inlet forthe cooling gas, the liner extending into the base.
 4. Aninternally-cooled flow-directing member for a turbomachine comprising,in combination, a hollow airfoil having an external wall defining aninternal chamber, a liner disposed in the airfoil and spaced from thewall, the liner having an inlet for a cooling gas and definingdistributed perforations for discharge of the gas toward the wall, theairfoil defining an outlet for the cooling gas at the tip of theairfoil, the wall bearing internal ribs extending spanwise of theairfoil and engaging the liner, the ribs increasing in height toward theairfoil tip so that cooling gas passages diverging toward the airfoiltip are defined by the wall and liner between the ribs, the innersurface of the wall having a relatively smooth finish for high heatemissivity and the outer surface of the liner having a relatively roughfinish for high heat absorptivity, the liner being made of a material ofrelatively high coefficient of thermal conductivity as compared to theairfoil; the airfoil having a base isolated from the flow passing theairfoil and including an inlet for the cooling gas, the liner extendinginto the base.